For many years, media undergoing transmission has included watermarks. Watermarks are embedded in the media outside the perception of the viewer. Audience measurement entities use the detection of watermarks to identify a source and/or ownership of presented media.
Watermarks embedded in transmitted media may repeat regularly throughout the duration of presentation. The watermarks are often repeated at regular intervals to improve accuracy of collected data and each watermark may include an identification and a timestamp.
The figures are not to scale. Wherever possible, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts.